What Size Generator Do I Need?

Businesses can benefit greatly by having portable industrial generators at their disposal. A towable unit is easy to transport to different jobsites. When you need to supply electricity at a construction site or power another remote location, a towable generator is ready to hitch to the back of a vehicle or mount onto a trailer.

Unlike permanent standby generators, portable industrial generators are designed for temporary installation and mobility. You can seamlessly transfer a portable generator between sites to fulfill short-term power needs.

Explore how to choose the right portable generator size and power capacity for your site.

What Is a Portable Industrial Generator?

It’s important to note that generators usually fall into three groups: standby, noncommercial portable and towable or mobile.

Standby

Standby generators satisfy permanent, energy-intensive power requirements. They provide backup power for larger areas like construction sites, office buildings, and hospitals in the case of a power outage. Standby generators remain in one spot, making transportation more of a challenge.

Noncommercial Portable

Noncommercial portable generators are compact units that fulfill more temporary, less energy-intensive power needs. For instance, you might take one to a campsite to charge a phone. You can also plug electric-powered appliances, tools, and extension cords into these small generators. These types of portable generators cannot power entire construction sites.

Towable or Mobile

Towable generator sets — also known as mobile or portable industrial generators — are lightweight and often equipped with wheels. They are designed to be mounted on trailers for easy transport around a site. Because they are smaller, mobile generators are typically quieter and often more eco-friendly, depending on the fuel. You’ll find towable generators at a range of locations, such as construction sites, stadiums, military bases, mines, and more.

Put simply, portable industrial generators offer the higher power capabilities of a standby option with the flexibility to tow it to various jobsites. Wherever you need power, a towable generator is ready to follow.

How Are Portable Generators Rated?

Mobile generator sets are typically rated by the following units:

• eKW: Also written as kWe, the eKW rating is the total generator output after the loss from mechanical to electrical energy — i.e. efficiency loss. It’s important to understand the generator’s eKW rating since equipment relies on this electrical power during operation. Electrical power is usually measured in watts or kilowatts (kW).
• kVA: Kilovolt-ampere (kVA) assesses real and reactive power, or apparent power. It measures how much power output the generator can produce for different applications. The higher the kVA rating, the more power the unit can generate. Multiplying the voltage by the amps can help you determine the kVA.

Types of Portable Industrial Generators

There are two common types of mobile generators:

• Diesel: A diesel generator provides substantial power for more robust applications, like powering drills and other heavy equipment. Portable industrial diesel generators can withstand large power loads and are often cost-effective and fuel-efficient.
• Natural gas: Natural gas generators use propane or natural gas to produce electricity. This electricity can be drawn from a direct line or through a natural gas tank.

Why Portable Generator Sizes Matter

Size is a key consideration in the process of buying a commercial portable generator. An incorrect size can damage the equipment, tools, and appliances drawing power — plus the generator itself.

Choosing a smaller mobile generator may be tempting due to the more affordable price tag. However, a generator that’s too small or lacks sufficient wattage won’t successfully power your remote jobsite. An undersized unit must work harder to meet your power needs, significantly straining the generator and shortening its service life.

If your commercial site puts too much strain on an undersized generator, it increases the risk of overloading. Overloading can cut off your power source and damage the generator permanently. In worst-case scenarios, overloading can cause an electrical fire or even an explosion.

At the same time, you want to avoid investing in an oversized portable industrial generator. Doing so could result in a potential waste of money, as you’re paying for more watts than you require. A unit that’s too large can also cause unnecessary power loss and even damage your equipment.

When comparing whether to choose a slightly larger or slightly smaller mobile generator set, it’s best to opt for slightly larger. Choosing a portable generator with extra wattage and power capacity is a safer route for the following reasons:

• Reduces the risk of damage and overheating.
• Provides more consistent performance.
• Increases employee safety.
• Extends the generator’s life span.

What Size Portable Generator Do You Need?

Follow these two steps to select the right portable industrial generator size for your applications.

1. Take Inventory of All Critical Devices

Start by making a list of everything your towable generator will need to power. Locate the starting and running wattage for each piece of equipment. You can find these wattages inscribed on the back, bottom, or nameplate. You can also consult your owner’s manual, either hard copy or online, to find this information.

2. Calculate the Total Power Requirement

Your total wattage requirement will help you select a suitable mobile generator size. Add the total running watts of all equipment you’ll need to power, plus your highest single starting watts. This calculation can help determine your power output needs.

Generators in the United States are normally rated in kW or kVA. Add up your equipment’s kW or kVA figures to calculate your total power capacity requirements. You should invest in a mobile generator that can withstand this total wattage without using 100% of it.

Additionally, manufacturers usually include performance charts with their units. Looking at these charts can help you estimate the appropriate portable generator size. Examine the different power ratings and find one that’s compatible with your applications.

Estimating Generator Sizes for Commercial Events

When planning events, you need to consider the logistical details of bringing a generator to your event space. Generally, the more power you need, the larger the generator must be. Factors like fuel delivery and storage, security, and connection points are crucial for seamless operation. Understanding the event’s specific power demands, including peak loads and continuous usage, will prevent costly oversizing or undersizing.

Here’s a guide to generator size by power:

• 20 kW–60 kW: These generators are usually towable behind a standard truck. They would take up one parking space and are suited to smaller gatherings, food trucks or supplemental power.
• 100 kW–300 kW: More powerful generators require dedicated delivery trucks and can take up two or more parking spaces. You’d also need to factor in a wide turning radius for drop-off. These units are ideal for medium-sized concerts, trade shows, or temporary facility power.
• 500 kW+: For major music festivals, you may need a generator with over 500 kW of power. These are usually the size of a shipping container, requiring need heavy-duty site access and specialist equipment to install. They often require crane assistance for placement.

As power increases, generators may produce more noise. For weddings, festivals, and other large events, you may need generators with sound-attenuated enclosures to control noise. Smaller mobile generators rated under 230 kVA can produce up to 72 dB(A), which is similar to a vacuum cleaner. Trailer-sized units tend to be much louder.

You should consider where you place generators to ensure ample airflow. Units typically need enough clearance on all sides to prevent overheating.

Another consideration is cabling. Your generator should be positioned close enough to your event space to minimize cable usage while being far enough away to minimize noise. Cables can be a trip hazard, so factor safety compliance into your cable placement and consider cable ramps to meet Americans with Disabilities Act (ADA) requirements.

Use an Electric Generator Size Calculator

When calculating what size generator you need for larger and more complex power requirements, using our electric generator size calculator can provide more accurate results than manual calculation.

Adding up wattages may work for simple lighting setups. When sizing a generator for heavy-duty HVAC systems or commercial event equipment, you need to account for special circumstances, like the surge in power when starting up all equipment.

An emergency generator size calculator can help you estimate specific needs by factoring in variables, like voltage and phase.

Generator Size Chart

Here are a few common use cases to help you find what size backup generator you need for your job.

Contact Thompson Power Systems for Reliable Portable Generators

At Thompson Power Systems, we proudly serve Alabama and the Florida Panhandle with high-quality power systems. If you need a dependable mobile power generator for a jobsite, we can help you find a solution.

We supply generator sets from Caterpillar, a brand renowned for its durability and performance. Our knowledgeable technicians will work with you to find a Cat^® generator compatible with your requirements.

Browse our assortment of mobile generator sets to find the solutions you’re looking for. If you have questions about choosing the ideal unit for your applications, contact us online or call 205-849-4361.